U.S. patent number 11,196,374 [Application Number 17/037,873] was granted by the patent office on 2021-12-07 for modeling method of stator winding air gap for temperature field analysis of ac traction motor.
This patent grant is currently assigned to Hunan University of Science and Technology. The grantee listed for this patent is Hunan University of Science and Technology. Invention is credited to Sijian Kuang, Ping Liu, Xiaoping Zhang, Zhu Zhang.
United States Patent |
11,196,374 |
Zhang , et al. |
December 7, 2021 |
Modeling method of stator winding air gap for temperature field
analysis of AC traction motor
Abstract
A modeling method of a stator winding air gap for temperature
field analysis of an AC traction motor includes: changing the width
of an air gap of a stator winding equivalent model according to a
set value of spacing; establishing a three-dimensional finite
element model of the AC traction motor with the stator winding air
gap; based on the three-dimensional finite element model of
different widths of the air gap, analyzing a temperature field to
obtain a temperature field distribution diagram of the AC traction
motor; carrying out the numerical fitting according to data in the
temperature distribution diagram to obtain a function relation
between the air-gap width and the temperature of the stator winding
equivalent model; and by measuring the actual temperature of a
motor stator winding, calculating an optimal air-gap width
corresponding to the modeling of the stator winding of the current
AC traction motor.
Inventors: |
Zhang; Xiaoping (Hunan,
CN), Liu; Ping (Hunan, CN), Kuang;
Sijian (Hunan, CN), Zhang; Zhu (Hunan,
CN) |
Applicant: |
Name |
City |
State |
Country |
Type |
Hunan University of Science and Technology |
Hunan |
N/A |
CN |
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Assignee: |
Hunan University of Science and
Technology (Xiangtan, CN)
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Family
ID: |
1000005979695 |
Appl.
No.: |
17/037,873 |
Filed: |
September 30, 2020 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20210013820 A1 |
Jan 14, 2021 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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PCT/CN2019/122279 |
Nov 30, 2019 |
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Foreign Application Priority Data
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Jan 10, 2019 [CN] |
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201910023474.0 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G06F
30/23 (20200101); H02P 23/14 (20130101); H02K
3/47 (20130101) |
Current International
Class: |
H02P
7/00 (20160101); H02P 23/14 (20060101); G06F
30/23 (20200101); H02K 3/47 (20060101) |
Field of
Search: |
;318/432 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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106096157 |
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Nov 2016 |
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CN |
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107844647 |
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Mar 2018 |
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CN |
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107885955 |
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Apr 2018 |
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CN |
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108733887 |
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Nov 2018 |
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CN |
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109753737 |
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May 2019 |
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CN |
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Other References
Modeling and Performance Optimization of Permanent Magnet Starter
Motor Base on Ansoft; Zhuang, Shengxian. cited by
applicant.
|
Primary Examiner: Chan; Kawing
Assistant Examiner: Agared; Gabriel
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of International Patent
Application No. PCT/CN2019/122279, filed on Nov. 30, 2019, which
claims the benefit of priority from Chinese Patent Application No.
201910023474.0, filed on Jan. 10, 2019. The content of the
aforementioned applications, including any intervening amendments
thereto, is incorporated herein by reference.
Claims
We claim:
1. A modeling method of a stator winding air gap for temperature
field analysis of an AC traction motor, comprising the following
steps: step 1): establishing a stator winding equivalent model
according to the structure of a stator winding of the AC traction
motor; step 2): based on the stator winding equivalent model
obtained in the step 1, determining the structure and the width of
an isolation layer between the model and a slot wall and a slot
wedge of a stator iron core; step 3): determining the structure and
the initial width of a corresponding insulation layer and the air
gap in the isolation layer according to the structure and the width
of the isolation layer obtained in the step 2, and based on the
structural parameters of other components of the motor,
establishing a three-dimensional finite element model of the AC
traction motor; step 4): carrying out the temperature field
analysis based on the three-dimensional finite element model of the
AC traction motor obtained in step 3 to obtain a temperature field
distribution diagram of the AC traction motor, and selecting the
temperature of a position on the surface of the stator winding
equivalent model as a to-be-measured value; step 5): changing the
air-gap width of the stator winding equivalent model according to
the set value of the spacing, respectively establishing the
three-dimensional finite element model of the AC traction motor,
solving the temperature field distribution of the AC traction motor
under different widths of the air gap, and respectively measuring
the temperature of the surface of the stator winding equivalent
model corresponding to the position in the step 4; step 6):
carrying out numerical fitting for N groups of air-gap widths and
corresponding temperature data of the stator winding equivalent
model obtained in the step 5 to obtain a calculation formula (8)
between the air-gap width and the temperature of the stator winding
equivalent model; h.sub.1(T)=.sub.ae.sup.bT+ce.sup.dT (8) in the
formula: h.sub.1(T) is a function of the winding air-gap width; T
is the temperature of one position on the surface of the winding
equivalent model; a, b, c and d are coefficients of the function of
the air-gap width; and e is a base number of a natural logarithm
function; step 7): measuring the actual temperature of the stator
motor winding corresponding to one position on the surface of the
equivalent model, and substituting the actual temperature into the
above calculation formula (8) to obtain the air-gap width
corresponding to the actual temperature, wherein the air-gap width
is used as the optimal air-gap width corresponding to the modeling
of the stator winding of the current AC traction motor; and step
8): by adopting the modeling method from steps 1-7, making an
actual AC traction motor comprises stator windings with the optimal
air-gap width.
2. The modeling method of the stator winding air gap for
temperature field analysis of the AC traction motor according to
claim 1, wherein in the step 1, during the modeling, multiple turns
of copper wires in the stator winding are equivalent to a single
turn of copper wire; a sectional area of the single turn of copper
wire is equal to the sectional area of the multiple turns of copper
wires, and the sectional shape of the single turn of copper wire is
identical to the stator slot shape; and the sectional area of the
single turn of copper wire is solved through the formula (1):
s.sub.1=n.pi.r.sub.1.sup.2 (1) in the formula: s.sub.1 is the
sectional area of the single turn of copper wire, r.sub.1 is a
radius of each turn of copper wire in the multiple turns of copper
wires of the stator winding, and n is the number of turns of the
multiple turns of copper wires of the stator winding.
3. The modeling method of the stator winding air gap for
temperature field analysis of the AC traction motor according to
claim 1, wherein in the step 2, the width of the isolation layer
between the equivalent model of the stator winding and the slot
wall and the slot wedge of the stator iron core is equal
everywhere, and the width of the isolation layer is calculated
through the formula (2): .function. ##EQU00009## in the formula: h
is the width of the isolation layer, r is the bottom radius of the
stator slot, and s.sub.2 is the sectional area of the stator
slot.
4. The modeling method of the stator winding air gap for
temperature field analysis of the AC traction motor according to
claim 1, wherein in the step 3, the initial width of the
corresponding air gap in the isolation layer is set as the
equivalent air-gap width of the single layer of copper wire in the
stator slot, which is specifically as follows: .pi..times.
##EQU00010## in the formula: h.sub.1 is the initial width of the
air gap in the isolation layer.
5. The modeling method of the stator winding air gap for
temperature field analysis of the AC traction motor according to
claim 1, wherein in the step 3, the initial width of the
corresponding insulation layer in the isolation layer is:
h.sub.2=h-h.sub.1 (4) in the formula: h.sub.2 is the initial width
of the insulation layer in the isolation layer.
6. The modeling method of the stator winding air gap for
temperature field analysis of the AC traction motor according to
claim 1, wherein the specific operation of the step 4 is as
follows: step 4-1): carrying out the grid partitioning for the
three-dimensional finite element model of the AC traction motor;
step 4-2): applying a heat source to the three-dimensional finite
element model of the AC traction motor after the grid partitioning;
step 4-3): setting boundary conditions and convective heat exchange
coefficients of the three-dimensional finite element model of the
AC traction motor; step 4-4): carrying out the finite element
calculation of the temperature field for the three-dimensional
finite element model to obtain the temperature field distribution
diagram of the AC traction motor, and selecting the temperature of
one position on the surface of the stator winding equivalent model
as the to-be-measured value.
7. The modeling method of the stator winding air gap for
temperature field analysis of the AC traction motor according to
claim 6, wherein the specific operation of the step 4-3 is as
follows: (a) setting the convective heat exchange coefficient among
a casing, heat radiating ribs and air as being equal everywhere;
(b) calculating a Reynolds number Re and a critical Reynolds number
Re.sub.l of the air gap between a stator and a rotor according to
the formula (5) and the formula (6);
.pi..times..times..times..delta..times..omega..times..times..delta.
##EQU00011## in the formulas: d.sub.1 is a radius of the rotor,
d.sub.2 is a radius of the stator, .delta. is a length of the air
gap between the stator and the rotor, .omega..sub.g is a rotation
speed of the rotor, and .nu. is kinematic viscosity of the air; (c)
based on the Reynolds number Re and the critical Reynolds number
Re.sub.l obtained in step b, determining the corresponding
convective heat exchange coefficient, and setting the convective
heat exchanging coefficient in the air gap between the stator and
the rotor as the calculated value.
8. The modeling method of the stator winding air gap for
temperature field analysis of the AC traction motor according to
claim 7, wherein in the step c, the conditions for determining the
corresponding convective heat exchange coefficient are: when
Re<Re.sub.l, this indicates that the air flow in the air gap is
laminar flow, and the convective heat exchange coefficient .alpha.
is assigned with the heat conducting coefficient of the air; when
Re>Re.sub.l, this indicates that the air flow in the air gap is
turbulent flow, and the convective heat exchange coefficient
.alpha. is calculated through the formula (7):
.alpha..times..times..times..lamda..delta. ##EQU00012## in the
formula: .lamda., is the heat conduction coefficient of the
air.
9. The modeling method of the stator winding air gap for
temperature field analysis of the AC traction motor according to
claim 1, wherein the set value of the spacing in the step 5 refers
to that the value of the spacing is determined by taking the
initial width of the air gap as an initial value and the width of
the isolation layer as a final value according to the numerical
fitting requirement, and the width of the air gap is gradually
increased from the initial value to the final value according to
the spacing.
Description
TECHNICAL FIELD
The present invention relates to the field of temperature field
analysis of an AC traction motor, and particularly relates to a
modeling method of a stator winding air gap for temperature field
analysis of the AC traction motor.
BACKGROUND OF THE PRESENT INVENTION
AC traction motors have been widely used in various fields because
of the advantages such as simple structure, reliable operation,
firmness, durability, large power and high rotation speed. The
temperature inside the AC traction motor is increased due to
various losses during the operation. If the temperature is too
high, the service life of the motor may be seriously affected.
Therefore, the temperature field inside the motor is analyzed to
instruct the optimized design of the motor structure, which has
important significance for lowering the temperature of the
motor.
In the prior art, since the temperature distribution condition of
all units inside the motor can be accurately reflected by adopting
the finite element method to analyze the temperature field of the
AC traction motor, and the analysis result is accurate, the finite
element method has been widely used. However, when the finite
element method is used to analyze the temperature field of the AC
traction motor, the accuracy requirement for the model is high; and
if the finite element model of the motor is established completely
according to the actual structure of the motor, there are various
problems such as model complexity, long modeling time, large
calculation workload and high requirement for the computer
performance, so the finite element method is difficult in
popularization. Therefore, generally the motor model is properly
simplified when the finite element method is actually used to
analyze the temperature field of the AC traction motor; and
particularly for the air gap in stator windings, due to the
irregularity of the air gaps among conducting wires and between a
relevant conducting wire and the slot wall of a stator in the
windings, the modeling of the winding air gap becomes very
difficult. Thus, the air gap is often neglected when in actual
modeling. Although this process simplifies the model, the accuracy
of the temperature field analysis is affected.
SUMMARY OF THE PRESENT INVENTION
For the above problems of the prior art, the present invention
provides a modeling method of a stator winding air gap for the
temperature field analysis of an AC traction motor, which is simple
in principle, high in algorithm precision and less in occupied
system resource.
The technical solutions provided by the present invention are as
follows:
The modeling method of the stator winding air gap for the
temperature field analysis of the AC traction motor includes:
changing the width of an air gap of a stator winding equivalent
model according to a set value of spacing, establishing a
three-dimensional finite element model of the AC traction motor
with the stator winding air gap, based on the three-dimensional
finite element model of different air-gap widths, analyzing the
temperature field to obtain a temperature field distribution
diagram of the AC traction motor, carrying out the numerical
fitting according to data in the temperature distribution diagram
to obtain a function relation between the air-gap width and the
temperature of the stator winding equivalent model, and by
measuring the actual temperature of a motor stator winding
corresponding to a position on the surface of the equivalent model,
calculating an optimal air-gap width corresponding to the modeling
of the stator winding of the current AC traction motor.
The air-gap width of the stator winding equivalent model is changed
according to the set value of spacing; the three-dimensional finite
element model of the AC traction motor with the stator winding air
gap is established; and the temperature field distribution diagram
of the AC traction motor is obtained by analyzing the temperature
field. The temperature field distribution of the AC traction motor
under different air-gap widths is solved; the numerical fitting is
carried out based on the air-gap width and the corresponding
temperature data of the stator winding equivalent model to obtain
the function relation between the air-gap width and the temperature
of the winding equivalent model; and by measuring the actual
temperature of the motor stator winding corresponding to a position
on the surface of its equivalent model, the air-gap width
corresponding to the actual temperature is calculated. The air-gap
width is used as the optimal air-gap width corresponding to the
modeling of the stator winding of the current AC traction
motor.
The modeling method of the stator winding air gap for the
temperature field analysis of the AC traction motor provided by the
present invention includes the following steps:
step 1): establishing the stator winding equivalent model according
to the structure of the stator winding of the AC traction
motor;
step 2): based on the stator winding equivalent model obtained in
the step 1, determining the structure and the width of an isolation
layer between the model and a slot wall and a slot wedge of a
stator iron core;
step 3): determining the structure and the initial width of a
corresponding insulation layer and the air gap in the isolation
layer according to the structure and the width of the isolation
layer obtained in the step 2, and based on the structural
parameters of other components of the motor, establishing a
three-dimensional finite element model of the AC traction
motor;
step 4): carrying out the temperature field analysis based on the
three-dimensional finite element model of the AC traction motor
obtained in step 3 to obtain the temperature field distribution
diagram of the AC traction motor, and selecting the temperature of
a position on the surface of the stator winding equivalent model as
a to-be-measured value;
step 5): changing the air-gap width of the stator winding
equivalent model according to the set value of the spacing,
respectively establishing the three-dimensional finite element
model of the AC traction motor, solving the temperature field
distribution of the AC traction motor under different widths of the
air gap, and respectively measuring the temperature of the surface
of the stator winding equivalent model corresponding to the
position in the step 4;
step 6): carrying out the numerical fitting for N groups of air-gap
widths and corresponding temperature data of the stator winding
equivalent model obtained in the step 5 to obtain a calculation
formula (8) between the air-gap width and the temperature of the
stator winding equivalent model: h.sub.1(T)=ae.sup.bT+ce.sup.dT
(8)
in the formula: h.sub.1(T) is a function of the winding air-gap
width; T is the temperature of one position on the surface of the
winding equivalent model; a, b, c and d are coefficients of the
function of the air-gap width; e is a base number of a natural
logarithm function; and specifically, a, b, c and d are determined
by the least square method;
step (7): measuring the actual temperature of the stator motor
winding corresponding to one position on the surface of the
equivalent model, substituting the actual temperature into the
above calculation formula (8) to obtain the air-gap width
corresponding to the actual temperature, wherein the air-gap width
is used as the optimal air-gap width corresponding to the modeling
of the stator winding of the current AC traction motor.
Preferably, in the step 1, during the modeling, multiple turns of
copper wires in the stator winding are equivalent to a single turn
of copper wire; a sectional area of the single turn of copper wire
is equal to the sectional area of the multiple turns of copper
wires, and the sectional shape of the single turn of copper wire is
identical to the stator slot shape; and the sectional area of the
single turn of copper wire is solved through the formula (1):
s.sub.1=n.pi.r.sub.1.sup.2 (1)
In the formula: s.sub.1 is the sectional area of the single turn of
copper wire, r.sub.1 is a radius of each turn of copper wire in the
multiple turns of copper wires of the stator winding, and n is the
number of turns of the multiple turns of copper wires of the stator
winding.
Preferably, in the step 2, the width of the isolation layer between
the equivalent model of the stator winding and the slot wall and
the slot wedge of the stator iron core is equal everywhere, and the
width of the isolation layer is calculated through the formula
(2):
.function. ##EQU00001##
In the formula: h is the width of the isolation layer, r is the
bottom radius of the stator slot, and s.sub.2 is the sectional area
of the stator slot.
Preferably, in the step 3, the initial width of the corresponding
air gap in the isolation layer is set as the equivalent air-gap
width of the single layer of copper wire in the stator slot, which
is specifically as follows:
.pi..times. ##EQU00002##
In the formula: h.sub.1 is the initial width of the air gap in the
isolation layer.
Preferably, in the step 3, the initial width of the corresponding
insulation layer in the isolation layer is: h.sub.2=h-h.sub.1
(4)
In the formula: h.sub.2 is the initial width of the insulation
layer in the isolation layer.
Preferably, the specific operation of the step 4 is as follows:
step 4-1): carrying out the grid partitioning for the
three-dimensional finite element model of the AC traction
motor;
step 4-2): applying a heat source to the three-dimensional finite
element model of the AC traction motor after the grid
partitioning;
step 4-3): setting boundary conditions and convective heat exchange
coefficients of the three-dimensional finite element model of the
AC traction motor;
step 4-4): carrying out the finite element calculation of the
temperature field for the three-dimensional finite element model to
obtain the temperature field distribution diagram of the AC
traction motor, and selecting the temperature of one position on
the surface of the stator winding equivalent model as the
to-be-measured value.
More preferably, the specific operation of the step 4-3 is as
follows: (a) setting the convective heat exchange coefficient among
a casing, heat radiating ribs and air as being equal everywhere;
(b) calculating a Reynolds number Re and a critical Reynolds number
Re.sub.l of the air gap between a stator and a rotor according to
the formula (5) and the formula (6);
.pi..times..times..times..delta..times..omega..times..times..delta.
##EQU00003##
In the formulas: d.sub.1 is a radius of the rotor, d.sub.2 is a
radius of the stator, .delta. is a length of the air gap between
the stator and the rotor, .omega..sub.g is a rotation speed of the
rotor, and .nu. is kinematic viscosity of the air; (c) based on the
Reynolds number Re and the critical Reynolds number Re/obtained in
step b, determining the corresponding convective heat exchange
coefficient, setting the convective heat exchanging coefficient in
the air gap between the stator and the rotor as the calculated
value, which is specifically as follows:
When Re<Re.sub.l, it indicates that the air flow in the air gap
is laminar flow, and the convective heat exchange coefficient
.alpha. is assigned with the heat conducting coefficient of the
air;
When Re>Re.sub.l, it indicates that the air flow in the air gap
is turbulent flow, and the convective heat exchange coefficient
.alpha. is calculated through the formula (7):
.alpha..times..times..times..lamda..delta. ##EQU00004##
In the formula: .lamda. is the heat conduction coefficient of the
air.
Preferably, the set value of the spacing in the step 5 refers to
that the value of the spacing is determined by taking the initial
width of the air gap as an initial value and the width of the
isolation layer as a final value according to the numerical fitting
requirement, and the width of the air gap is gradually increased
from the initial value to the final value according to the
spacing.
Compared with the prior art, the modeling method of the stator
winding air gap for the temperature field analysis of the AC
traction motor provided by the present invention has the following
advantages:
By adopting the modeling method of the stator winding air gap for
the temperature field analysis of the AC traction motor provided by
the present invention, the accurate model of the stator winding air
gap of the AC traction motor can be established, so that the
accuracy of the finite element model of the AC traction motor can
be effectively improved, and the accuracy of the temperature field
analysis of the AC traction motor can be effectively improved,
thereby providing beneficial instruction for the optimized design
of the structure of the AC traction motor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram of modeling in a stator slot of an AC
traction motor provided by embodiments of the present
invention;
FIG. 2 is a schematic diagram of a three-dimensional finite element
model of the AC traction motor established according to a stator
slot model provided by embodiments of the present invention;
FIG. 3 is a flow chart of a modeling method of a stator winding air
gap for temperature field analysis of the AC traction motor
provided by embodiments of the present invention;
FIG. 4 is a detailed flow chart of the modeling method of the
stator winding air gap for the temperature field analysis of the AC
traction motor provided by embodiments of the present
invention;
FIG. 5 is a schematic diagram of temperature field distribution of
the AC traction motor provided by embodiments of the present
invention; and
Table 1 shows air-gap width and its corresponding temperature data
of a stator winding equivalent model 1 provided by embodiments of
the present invention.
LIFT OF REFERENCE NUMERALS
1, stator winding equivalent model; 2, insulation layer 2; 3, air
gap between the surface insulation layer of the stator winding
equivalent model and a slot wall and a slot wedge of a stator iron
core; 4, slot wall; 5, slot wedge; 6, casing; 7, stator iron core;
8, stator wedge portion; 9, rotor conducting bar; 10, rotor iron
core; 11, air gap between the stator and the rotor; 12, rotor end
ring; 13, bearing; and 14, to-be-measured point.
DETAILED DESCRIPTION OF THE PRESENT INVENTION
Specific embodiments of the present invention are further described
below in detail in combination with the accompanying drawings. It
shall be understood that the specific embodiments described herein
are merely used to explain and interpret the present invention,
rather than limiting the present invention.
FIG. 1 is a schematic diagram of modeling in a stator slot of an AC
traction motor provided by embodiments of the present embodiment.
Referring to FIG. 1, the model is specifically as follows: the
inner end surface of a stator iron core 7 is provided with an
insulation slot; a stator coil assembly (serving as a stator
winding equivalent model 1) is arranged in the insulation slot; the
stator winding equivalent model 1 is provided with an isolation
layer; the isolation layer includes an insulation layer 2 and an
air gap 3 on the surface of the stator winding equivalent model 1;
the insulation layer 2 is arranged on the surface of the stator
winding equivalent model 1; the outer end surface of the insulation
slot is provided with two slot walls 4; a notch of the insulation
slot is provided with a slot wedge 5; and the air gap 3 is
respectively formed among the slot wall 4, the slot wedge 5 and the
insulation layer 2. The insulation layer 2 on the surface of the
stator winding equivalent model 1 refers to a polyimide insulation
layer, dipping varnish, a lacquer film and other insulation
materials wrapping the surface of multiple turns of copper wires of
the stator winding, which is equivalent to a single insulation
layer 2 on the surface of the stator winding equivalent model 1;
the air gap 3 refers to the air gap 3 among the multiple turns of
copper wires in the stator winding and between the copper wire and
the slot wall 4 and the slot wedge 5 of a stator iron core, which
is equivalent to the air gap 3 between the single turn of copper
wire and the slot wall 4 and the slot wedge 5 of the stator iron
core; and the width of the air gap 3 is set to be equal
everywhere.
FIG. 2 is a schematic diagram of a three-dimensional finite element
model of the AC traction motor provided by embodiments of the
present invention. FIG. 2 is one part of the finite element model
of the AC traction motor and at least includes the stator winding
equivalent model 1, the insulation layer 2 on the surface of the
stator winding equivalent model, the air gaps 3 between the
insulation layer on the surface of the stator winding equivalent
model and the slot wall and the slot wedge of the stator iron core,
the stator iron core 7, a stator wedge portion 8, a rotor iron core
10, a rotor conducting bar 9, a rotor end ring 12, a casing 6, a
bearing 13 and an air gap 11 between the stator and the rotor.
Specifically, the stator iron core 7 is fixedly assembled on the
casing 6. The stator winding equivalent model 1 is embedded in a
slot of the stator iron core 7. The surface of the stator winding
equivalent model 1 is covered with the insulation layer 2. The air
gaps 3 are formed between the insulation layer 2 and the slot wall
and slot wedge of the stator iron core 7. The stator wedge portion
8 is fixedly assembled onto a port of the slot of the stator iron
core 7. The rotor iron core 10 is fixedly assembled onto the
bearing 13. The rotor conducting bar 9 is fixedly assembled into
the slot of the rotor iron core 10. The rotor end ring 12 is
fixedly assembled onto an axial end surface of the rotor iron core
10.
Based on the above-mentioned modeling parts in the stator slot and
the three-dimensional finite element model of the AC traction
motor, a possible implementation of the modeling method of the
stator winding air gap for the temperature field analysis of the AC
traction motor is given below. Specifically, FIG. 3 and FIG. 4 are
a flow chart and a detailed flow chart of the modeling method of
the stator winding air gap for the temperature field analysis of
the AC traction motor provided by embodiments of the present
invention. The method includes the following steps (in the figures,
S1 indicates the step 1, S2 indicates the step 2, S3 indicates the
step 3, S4 indicates the step 4, S4-1 indicates the step 4-1, S4-2
indicates the step 4-2, S4-3 indicates the step 4-3, S4-4 indicates
the step 4-4, S5 indicates the step 5, S6 indicates the step 6, and
S7 indicates the step 7):
Step (1): the stator winding equivalent model 1 is established
according to the structure of the stator winding of the AC traction
motor;
During the modeling, multiple turns of copper wires in the stator
winding are equivalent to a single turn of copper wire, a sectional
area of the single turn of copper wire is equal to the sectional
area of the multiple turns of copper wires, and the sectional shape
of the single turn of copper wire is identical to the shape of the
stator slot. The sectional area of the single turn of copper wire
is solved through the formula (1): s.sub.1=n.pi.r.sub.1.sup.2
(1)
In the formula: s.sub.1 is the sectional area of the single turn of
copper wire, r.sub.1 is a radius of each turn of copper wire in the
multiple turns of copper wires of the stator winding, and n is the
number of turns of the multiple turns of copper wires of the stator
winding.
Step (2): based on the stator winding equivalent model 1 obtained
in step 1, the structure and the width of an isolation layer
between the model and the slot wall 4 and slot wedge 5 of the
stator iron core slot are determined, wherein the isolation layer
is a gap between the stator winding equivalent model 1 and the slot
wall 4 and slot wedge 5 of the stator iron core, and the width of
the isolation layer is equal everywhere. The width of the isolation
layer is calculated through the formula (2):
.function. ##EQU00005##
In the formula: h is the width of the isolation layer, r is the
bottom radius of the stator slot, and s.sub.2 is the sectional area
of the stator slot.
Step (3): the structure and the initial width of the insulation
layer 2 and the air gap 3 in the isolation layer are determined
respectively according to the structure and the width obtained in
step 2, and based on the structural parameters of other parts (i.e.
the casing 6, the stator iron core 7, the stator wedge portion 8,
the rotor conducting bar 9, the rotor iron core 10, the air gap 11
between the stator and the rotor, the rotor end ring 12, and the
bearing 13) of the motor, a three-dimensional finite element model
of the AC traction motor is established.
In the step 3, the corresponding air gap 3 in the isolation layer
is located between the insulation layer 2 and the slot wall 4 and
slot wedge 5 of the stator iron core, and its width is equal
everywhere. Its initial width is set as the equivalent air-gap
width of the single layer of copper wire in the stator slot, which
is specifically as follows:
.pi..times. ##EQU00006##
In the formula: h.sub.1 is the initial width of the air gap 3 in
the isolation layer.
In the step 3, the corresponding insulation layer 2 in the
isolation layer is closely fit to the outer surface of the stator
winding equivalent model 1, and its width is also equal everywhere.
Its initial width is as follows: h.sub.2=h-h.sub.1 (4)
In the formula: h.sub.2 is the initial width of the insulation
layer 2 in the isolation layer.
Step (4): the temperature field analysis is carried out according
to the three-dimensional finite element model of the AC traction
motor obtained in step 3 to obtain a temperature field distribution
diagram of the AC traction motor, and the temperature of a position
on the surface of the stator winding equivalent model is selected
as a to-be-measured value, which is specifically as follows:
Step (4-1): the grid partitioning is carried out for the
three-dimensional finite element model of the AC traction
motor.
Step (4-2): a heat source is applied to the grid-partitioned
three-dimensional finite element model of the AC traction motor.
Specifically, the heat source refers to the loss generated during
the running of the AC traction motor. The loss of the AC traction
motor includes the copper loss of the stator winding, aluminum loss
of the rotor conducting bar, iron loss in the iron core and
mechanical loss.
Step (4-3): boundary conditions and convective heat exchange
coefficients of the three-dimensional finite element model of the
AC traction motor are set, which are specifically as follows: (a)
the convective heat exchange coefficient among the casing, heat
radiating ribs and the air is set as being equal everywhere; (b) a
Reynolds number Re and a critical Reynolds number Re.sub.l of the
air gap between the stator and the rotor are calculated according
to the formula (5) and the formula (6);
.pi..times..times..times..delta..times..omega..times..times..delta.
##EQU00007##
In the formulas: d.sub.1 is a radius of the rotor, d.sub.2 is a
radius of the stator, .delta. is a length of the air gap between
the stator and the rotor, .omega..sub.g is a rotation speed of the
rotor, and .nu. is kinematic viscosity of the air; (c) based on the
Reynolds number Re and the critical Reynolds number Re.sub.l
obtained in step b, the corresponding convective heat exchange
coefficient is determined, and the convective heat exchanging
coefficient in the air gap between the stator and the rotor is set
to be the calculated value, which is specifically as follows:
When Re<Re.sub.l, it indicates that the air flow in the air gap
is laminar flow, and the convective heat exchange coefficient
.alpha. is assigned with the heat conducting coefficient of the
air, and .alpha.=0.0267 W/m K;
When Re>Re.sub.l, it indicates that the air flow in the air gap
is turbulent flow, and the convective heat exchange coefficient
.alpha. is calculated through the formula (7):
.alpha..times..times..times..lamda..delta. ##EQU00008##
In the formula: .lamda., is the heat conduction coefficient of the
air.
The boundary conditions are specifically set as follows: boundary
temperature of the AC traction motor casing is set; a heat
radiating mode of two axial symmetric side surfaces of the
three-dimensional finite element model of the AC traction motor is
set; and the boundary temperature of the AC traction motor casing
can be set as the ambient temperature, and the heat radiating mode
of the two axial symmetric side surfaces of the three-dimensional
finite element model of the AC traction motor is set as heat
insulation.
Step (4-4): the finite element calculation of the temperature field
is carried out for the three-dimensional finite element model to
obtain the temperature field distribution diagram of the AC
traction motor. Specifically, FIG. 5 is a schematic diagram of the
temperature field distribution of the AC traction motor provided by
embodiments of the present invention, and the temperature of a
to-be-measured point 14 on the surface of the winding equivalent
model is selected as the to-be-measured value.
Step (5): the width of the air gap 3 of the stator winding
equivalent model 1 is changed according to certain spacing; then
the three-dimensional finite element model of the AC traction motor
is respectively established; the temperature field distribution of
the AC traction motor under different widths of the air gap 3 is
solved, and the temperature on the surface of the stator winding
equivalent model 1 corresponding to the to-be-measured point 14 in
the step 4 is measured; and the width of the air gap 3 of the
winding equivalent model 1 is changed according to certain spacing,
which refers to that the initial width of the air gap 3 is used as
the initial value, the width of the isolation layer is used as the
final value, and the spacing is determined according to the
numerical fitting requirement. The width of the air gap 3 is
gradually increased from the initial value to the final value.
Specifically, Table 1 shows 8 groups of air-gap widths and
corresponding temperature data of the stator winding equivalent
model 1 provided by embodiments of the present invention. For
example, the initial width of the air gap 3 is 0.1 mm, and the
width of the isolation layer is 0.45 mm, so that the width range of
the air gap 3 of the winding equivalent model 1 is 0.1-0.45 mm. In
this width range of the air gap 3 of the winding equivalent model
1, the width data of the air gaps 3 of 8 winding equivalent models
1 is collected according to the interval of 0.05 mm, and the
three-dimensional finite element model of the AC traction motor is
respectively established to solve the temperature field
distribution of the AC traction motor under different widths of the
air gap 3. The corresponding temperature data is measured at the
to-be-measured point 14 on the surface of the stator winding
equivalent model 1.
Step (6): the numerical fitting is carried out for N groups of
air-gap widths and corresponding temperature data of the stator
winding equivalent model 1 obtained in step 5. The numerical
fitting method prefers the least square method. The calculation
formula (8) between the width of the air gap 3 and the temperature
of the stator winding equivalent model 1 is obtained as follows:
h.sub.1(T)=ae.sup.bT+ce.sup.dT (8)
In the formula: h.sub.1(T) is a function of the winding air-gap
width; T is the temperature of one position on the surface of the
winding equivalent model; a, b, c and d are coefficients of the
function of the air-gap width and are determined by the least
square method; e is the base number of a natural logarithm
function.
Specifically, according to the data in Table 1, and based on the
least square method, by using MATLAB analysis software, the
coefficients a, b, c and d can be calculated respectively as:
a=0.1737; b=0.007736; c=-217.7; d=-0.07486.
Step (7): the actual temperature of the motor stator winding
corresponding to the to-be-measured point 14 on the surface of its
equivalent model is measured, and the actual temperature is
substituted into the above calculation formula (8) to obtain the
air-gap width corresponding to the actual temperature. The air-gap
width is used as the optimal air-gap width corresponding to the
modeling of the stator winding of the current AC traction
motor.
TABLE-US-00001 TABLE 1 Air-gap 0.10 0.15 0.20 0.25 0.30 0.35 0.40
0.45 width (mm) Temperature 90.340 93.284 95.845 99.340 104.550
109.900 118.000 127.710 data (.degree. C.)
The above only describes preferred embodiments of the present
invention, rather than limits the present invention in any form.
Although the present invention has already been disclosed with the
preferred embodiments, the present invention is not limited
thereto. Therefore, any simple changes, equivalent variations and
modifications made to the above embodiments based on the technical
essence of the present invention without departing from the content
of the technical solutions of the present invention shall fall
within the protection scope of the technical solutions of the
present invention.
* * * * *